.\"
.\" Copyright (C) 2014 Red Hat, Inc. All Rights Reserved.
.\" Written by David Howells (dhowells@redhat.com)
.\"
.\" This program is free software; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public Licence
.\" as published by the Free Software Foundation; either version
.\" 2 of the Licence, or (at your option) any later version.
.\"
.TH "SESSION KEYRING" 7 "19 Feb 2014" Linux "Kernel key management"
.\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
.SH NAME
session_keyring \- Session shared process keyring
.SH DESCRIPTION
The
.B session keyring
is a keyring used to anchor keys on behalf of a process.  It is typically
created by the \fBpam_keyinit\fP module when a user logs in and a link will be
added that refers to the \fBuser keyring\fP.
.P
A special serial number value, \fBKEY_SPEC_SESSION_KEYRING\fP, is defined that
can be used in lieu of the calling process's session keyring's actual serial
number.
.P
From the keyctl utility, '\fB@s\fP' can be used instead of a numeric key ID in
much the same way.
.P
A process's session keyring is inherited across clone(), fork() and vfork() and
is retained across execve() - even when the target executable is setuid or
setgid.  The session keyring will be destroyed when the last process that
refers to it exits.
.P
If a process doesn't have a session keyring when it is accessed, then, under
certain circumstances, the \fBuser session keyring\fR will be attached as the
session keyring and under others a new session keyring will be created.
.SH SPECIAL OPERATIONS
The keyutils library provides a number of special operations for manipulating
session keyrings:
.IP \fBkeyctl_join_session_keyring\fP()
This operation allows the caller to change their session keyring.  The caller
can join an existing keyring by name, create a new keyring of the name given or
ask the kernel to create a new session keyring with the name "_ses".
.IP \fBkeyctl_session_to_parent\fP()
This operation allows the caller to set the parent process's session keyring to
the same as their own.  For this to succeed, the parent process must have
identical security attributes and must be single threaded.
.P
These operations are also exposed through the keyctl utility as:
.P
.RS
\fBkeyctl\fP session
.br
\fBkeyctl\fP session - [<prog> <arg1> <arg2> ...]
.br
\fBkeyctl\fP session <name> [<prog> <arg1> <arg2> ...]
.RE
.P
and:
.P
.RS
\fBkeyctl\fP new_session
.RE
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.SH SEE ALSO
.BR keyctl (1),
.br
.BR keyctl (3),
.br
.BR keyctl_join_session_keyring (3),
.br
.BR keyctl_session_to_parent (3),
.br
.BR pam_keyinit (8),
.br
.BR keyrings (7),
.br
.BR thread-keyring (7),
.br
.BR process-keyring (7),
.br
.BR user-keyring (7),
.br
.BR user-session-keyring (7)
.br
.BR persistent-keyring (7)
